1. Field of the Invention
The present invention generally relates to heating, ventilating, and air conditioning systems (HVAC systems), and more specifically to a filter core having an expandable air filter media.
2. Description of Related Art
HVAC equipment, such as furnaces, air conditioners, heat pumps and air handlers, usually include some type of air filter for removing dust and other particles from the air. A blower typically forces the air through the filter before the air is conveyed to a room or other area of a building served by the HVAC equipment.
One type of filter, known as a filter core, comprises an outer frame containing an air permeable material or filter media. The core then is removably inserted in a filter casing that holds the filter core in the main air passage of the HVAC equipment or associated ductwork. Restricted porosity of the filter media allows the filter to catch air contaminants as air passes through the filter. As the filter becomes dirty, the filter core and/or filter media is periodically cleaned or replaced.
One example of a filter casing for holding filter cores is disclosed in U.S. Pat. No. 3,630,008. The casing includes hinged side panels that provide access for replacing the filter cores.
To reduce the frequency of changing or cleaning the filter or to reduce the filter""s airflow resistance, the filter media can be provided with a large surface area. However, this may lead to an oversized filter frame, which can be expensive and can be difficult to install in areas of limited space. So, the filter media is often pleated or corrugated to increase its surface area without increasing the overall size of the filter frame.
Typical examples of filters with a corrugated filter media are disclosed in U.S. Pat. Nos. 1,982,639; 2,393,419; 2,739,667 and 3,246,456. The ""639 patent discloses a filter media that is fed from one storage roller onto another as a series of staggered rollers guides a dust-collecting portion of the media in a zigzag pattern across the main air passage. It appears that each roller alone has enough capacity to store the entire filter media. This is apparently so that one roller can hold a complete roll of clean media, and later, the other roller can collect the entire roll after the media has passed across the air passage. Consequently, the filter assembly is quite bulky, as its total storage area is at least twice the volume of the filter media.
A common drawback of current filters is that they are usually of fixed predetermined sizes to fit specific filter frames, filter casings or air passageways. This creates a problem for filter manufacturers and dealers, as they may need to carry a large inventory of filters to match the numerous models of HVAC equipment. Such an inventory may require a significant amount storage space, as there are tendencies or advantages of making filters large to reduce the frequency at which they need to be changed and to reduce the filter""s airflow resistance, as already explained.
To overcome the drawbacks of current air filters, it is an object of the invention to provide a corrugated filter media that can be used in various sized filter frames. Another object of the invention is to enable parts dealers to reduce their inventory of filters and to allow the dealers to supply the right filter media without having to know an exact size of a particular piece of HVAC equipment.
Another object of the invention is to provide a filter frame with integral living hinges that enable a relatively flat frame to fold into a more box-like shape.
Another object is to provide a filter media with side panels that connect to a filter frame, such that together the filter media and filter frame comprise a box-like structure.
Another object is to provide a filter frame with a storage chamber for storing unused pleats of a corrugated filter media.
Yet, another object is to provide a filter frame that includes a pivotal saw tooth rack for supporting a corrugated filter media.
A further object is to provide a filter frame with a channel that helps support a side panel of a filter media.
A still further object is to provide a filter core that once installed in a filter casing is substantially stationary to avoid the maintenance that is often associated with moving parts.
Another object is to provide a filter frame with a tie rod that helps hold a pivotal saw tooth rack in its proper position.
Another object is to have a living hinge couple the tie rod to filter frame.
These and other objects of the invention are provided by a filter assembly that includes a corrugated filter media, wherein some pleats of the media are disposed in a main airflow passageway, and other pleats are folded more compactly and stored further away from the main flow of air.